In the current field of injection molds, primarily those of considerable size (i.e., molds for the automotive sector or the like) and for obtaining plastic molded parts, the configuration of which has negative zones that cannot be molded by the conventional removal system, requires the use of skids having angular movement associated with the mold, such that the demolding of these negative portions is facilitated during the removal process.
Normally and depending on the negative to be molded, the path of these skids does not have to be the same as the path of the ejectors demolding the corresponding part. For this reason, most of these molds require using a double set of ejection plates.
These ejection plates use the same shifting movement for both groups of ejection plates, but by means of duly incorporated mechanisms, the present invention allows the first group of ejection plates to remain stationary after certain travel, while the second group continues to move to the travel limit necessary for complete removal of the molded part.
The first group of ejection plates usually incorporates all the mechanisms for angular movement, whereas the second group of ejection plates incorporates all the ejectors that enable complete ejection of the corresponding molded product.
This system, primarily brought about as a result of the effort needed to actuate one or several angular demolding elements, requires suitably sized ejection plates
As they are mechanisms for angular movement, the space required for their installation in many cases makes searching for more or less burdensome alternatives necessary due to the space needed to reinforce the efforts required in each case. Consequently, larger overall mold sizes are required, with the subsequent material costs and machining hours. In many cases an injection machine with a larger capacity is also necessary due only to mold sizes and not the weight of the part.
All this considerably increases the cost of the mold and often the machines which enable machining thereof as well, which must be duly suited to these needs.
Since the molds are large, these negative portions usually also take up a significant portion of the shape to be molded, and in these cases the incorporation of cooling elements is essential to speed up cooling of the mass molded by molten plastic injection.
Therefore, the part to be demolded must be cooled before the ejection process since at the time of injection, the material enters the mold cavity in a semi-pasty state, and to be ejected through the ejectors the material must be cold and rigid.
The cooling process in plastic molds is achieved by means of internal circuits machined in the mold, through which cold water circulates, thereby achieving a jump in temperature speeding up hardening of the molded part.
The device described in document ES 2398793 A1, which belongs to the same owner as the present application and is herein incorporated as a reference, was designed to solve these problems.
The objective of the device according to the present invention with respect to the device described in said document is to reduce the volume of the device, such that it does not take up too much space when assembled inside the mold.